Endoscope treatment tool

1. An endoscopic treatment tool comprising:

a longitudinal sheath having a distal end, a proximal end, a length, and a thickness that is orthogonal to the length, the sheath forming an inner cavity that extends from the distal end to the proximal end along the length of the sheath;

a support portion attached to the distal end of the sheath, the support portion comprising an engaging portion that has an annular shape and is disposed to protrude from an inner circumferential surface of the support portion;

a forceps member having a pair of facing surfaces that are supported so as to be rotatable around a rotation axis member on the support portion, the pair of facing surfaces being configured to be opened and closed and being disposed so as to protrude from the rotation axis member toward a distal end side of the endoscopic treatment tool;

a linear portion that is at least partially disposed within the cavity of the sheath and is capable of advancing and retracting along a direction of the length of the sheath to open and close the pair of facing surfaces;

a stopper that is disposed within the cavity of the sheath and is capable of advancing and retracting along the direction of the length of the sheath, the stopper being capable of restricting advancement of the linear portion when the stopper abuts against the engaging portion such that the pair of facing surfaces is retained in an open state at an opening angle; and

a moving mechanism that is configured to move at least part of the linear portion along the direction of the length of the sheath independently of the stopper by a predetermined operation of a user;

wherein:

the linear portion is configured to advance and retract along the direction of the length of the sheath together with the stopper to open and close the pair of facing surfaces until the stopper abuts against the engaging portion, and

the at least part of the linear portion is configured to advance and retract along the direction of the length of the sheath independently of the stopper to adjust a distance between a distal end of the linear portion and a distal end of the stopper when the stopper abuts against the engaging portion.

2. The endoscopic treatment tool according to claim 1 , wherein:

the linear portion includes:

a first linear member that forms a distal end portion of the linear portion, a distal end of the first linear member being connected to at least one of the facing surfaces, and a proximal end of the first linear member being movably connected to the stopper, and

a second linear member that is disposed proximally of the first linear member, a distal end of the second linear member being fixed to the stopper,

the moving mechanism includes:

a male threaded portion that is formed in the proximal end of the first linear member, the male threaded portion having an axial line of the first linear member as a spiral axis, and

a female threaded portion that is formed in the distal end of the stopper, the female threaded portion being threadedly engaged with the male threaded portion,

the moving mechanism is configured to distally or proximally move the first linear portion independently of the stopper along the direction of the length of the sheath by rotating the stopper around the axial line to adjust a length of the male threaded portion that is threadedly engaged with the female threaded portion,

when the first linear portion is moved distally along the direction of the length of the sheath independently of the stopper, the distance between the distal end of the linear portion and the distal end of the stopper increases, and the length of the male threaded portion that is threadedly engaged with the female threaded portion decreases, and

when the first linear portion is moved proximally along the direction of the length of the sheath independently of the stopper, the distance between the distal end of the linear portion and the distal end of the stopper decreases, and the length of the male threaded portion that is threadedly engaged with the female threaded portion increases.

3. The endoscopic treatment tool according to claim 2 , further comprising:

a first link member having a distal end and a proximal end, the distal end of the first link member being rotatably connected to a portion of one facing surface of the pair of facing surfaces, the portion of the one facing surface being disposed proximally of the rotation axis member;

a second link member having a distal end and a proximal end, the distal end of the second link member being rotatably connected to a portion of an other facing surface of the pair of facing surfaces, the portion of the other facing surface being disposed proximally of the rotation axis member; and

a second rotation axis member that rotatably connects the proximal end of the first link member and the proximal end of the second link member,

wherein:

the first linear member is connected to the second rotation axis member, and the stopper has a contact surface that comes into contact with a surface of the engaging portion when the stopper abuts against the engaging portion.

4. The endoscopic treatment tool according to claim 2 , wherein:

the opening angle of the pair of facing surfaces in the open state is set to be a predetermined value when the linear portion is moved proximally to a reference position at which the distance between the distal end of the linear portion and the distal end of the stopper is decreased to a minimum value; and

the opening angle of the pair of facing surfaces in the open state is increased to be larger than the predetermined value when the linear portion is moved distally with respect to the reference position such that the distance between the distal end of the linear portion and the distal end of the stopper is increased.

5. The endoscopic treatment tool according to claim 1 , wherein:

the stopper includes a through hole which penetrates in the direction of the length of the sheath and through which the linear portion is inserted,

the moving mechanism has:

a concave portion that is formed on one of an outer circumferential surface of the linear portion and an inner circumferential surface of the through hole, and

a convex portion that is formed on an other of the outer circumferential surface of the linear portion and the inner circumferential surface of the through hole,

the convex portion is configured to engage with the concave portion,

the linear portion is configured to move along the direction of the length of the sheath independently of the stopper when at least a predetermined amount of force is applied to the stopper and the linear portion along the direction of the length of the sheath and the stopper abuts against the engaging portion,

the convex portion is configured to be elastically deformed such that the convex portion is not engaged with the concave portion when the linear portion is moved along the direction of the length of the sheath independently of the stopper,

the convex portion is configured to be in sliding contact with the one of the outer circumferential surface of the linear portion and the inner circumferential surface of the through hole when the convex portion is not engaged with the concave portion,

a distal end portion of the linear portion is in a reference position with respect to the stopper when the concave portion is engaged with the convex portion, and

the distal end portion of the linear portion is in a distal end position with respect to the stopper when the linear portion is moved along the direction of the length of the sheath toward the distal end side of the endoscopic treatment tool independently of the stopper such that the convex portion is not engaged with the concave portion.

6. The endoscopic treatment tool according to claim 5 , further comprising: an inner sheath that extends proximally from a proximal end of the stopper.

7. The endoscopic treatment tool according to claim 5 , further comprising:

a first link member having a distal end and a proximal end, the distal end of the first link member being rotatably connected to a portion of one facing surface of the pair of the facing surfaces, the portion of the one facing surface being disposed proximally of the rotation axis member;

a second link member having a distal end and a proximal end, the distal end of the second link member being rotatably connected to a portion of an other facing surface of the pair of facing surfaces, the portion of the other facing surface being disposed proximally of the rotation axis member; and

a second rotation axis member that rotatably connects the proximal end of the first link member and the proximal end of the second link member,

wherein:

the distal end of the linear portion is connected to the second rotation axis member,

the stopper has a contact surface that comes into contact with a surface of the engaging portion when the stopper abuts against the engaging portion, and

a distance from the second rotation axis member to the contact surface of the stopper increases as the distal end of the linear portion moves toward the distal end side of the endoscopic treatment tool.

8. The endoscopic treatment tool according to claim 1 , wherein:

the linear portion includes:

a first linear member that forms a distal end portion of the linear portion, a distal end of the first linear member being connected to at least one of the facing surfaces, and a proximal end of the first linear member being connected to the stopper, and

a second linear member that is disposed proximally of the first linear member, a distal end of the second linear member being fixed to the stopper,

the moving mechanism includes:

a male threaded portion that is formed in the proximal end of the first linear member, the male threaded portion having an axial line of the first linear member as a spiral axis, and

a female threaded portion that is formed in the distal end of the stopper, the female threaded portion being threadedly engaged with the male threaded portion,

the moving mechanism is configured to move the first linear portion distally with respect to the stopper along the direction of the length of the sheath by rotating the stopper around the axial line to adjust a length of the male threaded portion that is threadedly engaged with the female threaded portion,

the distance between the distal end of the linear portion and the distal end of the stopper is decreased when the length of the male threaded portion that is threadedly engaged with the female threaded portion is increased, and

the distance between the distal end of the linear portion and the distal end of the stopper is increased when the length of the male threaded portion that is threadedly engaged with the female threaded portion is decreased.